The present invention relates to thermal printing systems, and more particularly, to a thermal printing system in which printing speed is maximized by electronically controlling the temperature of the print elements in accordance with the varying dot pattern being printed.
Thermal printers are widely used in devices such as electronic adding machines, cash registers, and home computer systems. Typically they print alphanumeric information in dot matrix form on paper coated with a thermally sensitive material. The print head elements comprise thick film deposited resistors through which current is passed in pulses to heat the thermally sensitive material to a temperature at which it changes color, thereby causing dots to be printed on the paper.
The speed of printing in a thermal printer is limited by the speed at which the individual print elements in the print head can be heated to a temperature above the thermal coating threshold temperature and then cooled to below the thermal coating threshold temperature during the printing of each dot. In some environments, such as a ticket vending machine for a mass transit system, it would be desirable to provide a thermal printing system capable of rapidly printing information on tickets over a long period of time with high reliability and low power consumption.